SMD-01B

Optical Encoder IC

SMD-01B Reflective type Optical Encoder IC
Smallest in its class: Can be mounted in tiny spaces
High accuracy:< 1μm high resolution with external interpolation circuit
Wide operating range: 3.13 to 5.25V supply voltage

1. SMD-01B Overview
The SMD-01B is the world’s smallest encoder IC in its class, incorporating a LED light source and an OEIC
(Opto-Electric Integrated Circuit) in a single surface-mounted-device package. It employs an optical sensor array that
greatly reduces signal degradation problems due to variations in mounting position. It delivers high-accuracy position
detection even when mounted using reflow methods. It is ideal for various applications that require the following
characteristics.
[Features]Miniature clear molded package 5.3mm (W) × 4.3mm (L) × 1.68mm (H)High-accuracy two-phase differential analog output
A-phase/B-phase analog, sine wave outputs
Also, inverted differential outputs for noise cancellation
20μm output signal period (fixed) High S/N ratio and superior Lissajous characteristic for better than sub-micron
resolution, in combination with external interpolation circuit
Built-in LED light source 3-step adjustable light intensity
Wide supply voltage range 3.13 to 5.25 V
Low current consumption 12.2mA (typ)Easy positioning/installation
Reflow mounting (*confirm suitability of reflow conditions)[Typical Applications]Miniature actuators, piezo-actuators
Precision stages
Distance measurement equipment, angle measurement equipment, linear gauges
Galvanometers
Optical axis control of laser light
Chip mounters, PCB/FPC substrate processing, IC handlers & FA mounting/processing
Motion control of industrial robots and consumer robots
Position/speed control in applications requiring miniaturization and high accuracy

SMD-01B Application Note
ANE240010-E001

2024.03
1/12

SMD-01B

Optical Encoder IC

2. Typical SMD-01B Encoder Configurations
2.1. Linear Encoder Configuration and Alignment

A linear encoder can be constructed using the SMD-01B and a linear scale.
The linear scale pattern width can be made as narrow as ±0.5mm when the linear scale pattern width center correctly
matches the SMD-01B optical center (Y orientation in the following figure). The pattern width should be chosen after
careful evaluation.
The optical center point is a point midway between the SMD-01B built-in LED source optical center and the lightsensor photodiode center.

[TOP VIEW]

SMD-01B Application Note
ANE240010-E001

2024.03
2/12

SMD-01B

Optical Encoder IC

2.2. Rotary Encoder Configuration and Alignment

A rotary encoder can be constructed using the SMD-01B and a disk-shaped rotary scale.
For a rotary encoder, the SMD-01B optical center point must be correctly positioned in the center of the rotary scale
horizontally and vertically, as shown in the following figure.

SMD-01B Application Note
ANE240010-E001

2024.03
3/12

SMD-01B

Optical Encoder IC

2.3. Advantages of Small Diameter Rotary Encoders
When a general-purpose encoder IC is used for a rotary encoder, the output amplitude tends to decrease because theencoder IC is designed to receive parallel reflected light of the correct period whereas the reflected light isfan-shaped due to the scale pattern. As the output amplitude decreases, operation at high interpolation factors becomesdifficult and high resolution increasingly difficult to obtain.
The SMD-01B, however, has a miniature light receiver with a short scale pitch that reduces the effects of reflected
light from fan-shaped rotary scales. Consequently, it can be employed in miniature, lightweight rotary encoders. It also
helps to reduce the rotational inertia of parts with attached encoder or scale for better system miniaturization andweight reduction.
Large difference between reflected
light and photo diode array shape.

Encoder with long scale
pitch and large photo
diode surface area

Output waveform amplitude drop: large
Photo diodearray
Reflected light fromrotary scale

SMD-01B

Photo diodearray

Output waveform amplitude drop: small

Reflected light fromrotary scale

The following table shows typical signal amplitudes for a small-diameter rotary encoder configuration using the
SMD-01B.

SMD-01B output amplitude using small-diameter rotary scale (reference data)
Scale diameter Scale pattern width
CPR
SMD-01B output amplitude (%)
(mm)
(mm)
(pulse count / revolution) [linear scale representing 100% amplitude] *2
9.5
0.5≒1500*1
95
*1
6.4
0.5
≒1000
80
5.1
0.4
≒800*160*1: These values are achieved by converting A/B phase analog signals to a binary code with a comparator circuit.
The CPR values are calculated using the following equation.

Resolution equivalent to 4 times as much as CPR above is obtained by counting rising/falling of A/B phases
respectively. Higher resolution according to interpolation factors is realized by using an external interpolation circuit.
*2: Rotary scale mounting position is individually adjusted to obtain largest signal amplitude. Values in the table areexample.
When using a small-diameter rotary scale, effect of mounting conditions on amplitude and phase difference isgreater than a linear scale. Individualized alignment is recommended to obtain better product characteristics.

SMD-01B Application Note
ANE240010-E001

2024.03
4/12

SMD-01B

Optical Encoder IC

2.4. Scales for SMD-01B
As described, a linear/rotary encoder can be constructed in combination with a linear scale or rotary scale.
Scales are not provided with the SMD-01B; they must be acquired separately. The following manufacturers can supply
scales that can be used with the SMD-01B.

2.4.1. Glass scale
Generally, glass scales using a glass substrate are most suitable.
The following manufacturer can supply both linear and rotary scales.
[Glass scale manufacturer]
Koshibu Precision Co.,Ltd.
2-20-11 Hayamiya, Nerima-ku, Tokyo 179-0085, Japan
TEL: (03) 3934-2670
URL: https://www.koshibu.co.jp
E-mail: kakizawa@koshibu.co.jp(Attn: YUTAKA KAKIZAWA)
Note that the SMD-01B output signal is designed for a detection period of 20μm so the scale should be 20μm pitch(reflective surface 10μm / non-reflective surface 10μm). Detection period cannot be changed even if the scale pitch ischanged.
However, the SMD-01B high-accuracy analog output signals can be configured to work with arbitrary resolution using
external interpolation circuits and counters. With a glass scale, it is possible to achieve resolutions of 0.1μm or betterwith careful design.

SMD-01B Application Note
ANE240010-E001

2024.03
5/12

SMD-01B

Optical Encoder IC

3. Operating Principles and SMD-01B Characteristics
The SMD-01B optical encoder IC operates using the diffraction image projection method. The main structuralcomponents are comprised by the SMD-01B built-in LED and OEIC, and an external scale.
The encoder functions by emitting light from the LED onto a scale. Diffracted light from the scale is picked up by the
OEIC positioned at the focal point of the diffracted light. The periodic patterns of shade and light are detected in orderto determine the position on the scale.
The OEIC contains an array of light sensors (photodiodes) arranged in an array at precisely 1/4 the pitch of thediffracted light in order to observe the patterns in the diffracted light. The light receiver photodiode sensor arraysimultaneously observes the portion of the diffracted light and outputs an average value signal. The SMD-01B isdesigned with A-phase and B-phase outputs used to counterbalance the effects of variations from perfect parallel
movement as the photodiode array moves relative to the scale.

These abilities provide the SMD-01B with the following features:
1) Reduces susceptibility to output signal effects caused by localized defects or dirt on the surfaces of the SMD-01B
and scale.
2) Reduces susceptibility to SMD-01B output amplitude variation due to positioning errors.
Reference data for the output amplitude variation due to positioning errors are provided in the device datasheet.
However, conditions of optimum optics of this product may vary due to mounting tolerance of optical elements, so
thorough evaluation is needed to set the conditions. It is recommended to check the output signals while positioning theencoder particularly when using a small-diameter rotary scale, which effect of alignment conditions on signal amplitude
and phase difference is greater than a linear scale, or an external interpolation circuit to achieve resolutions of 1μm or
better.

4. Reference Information about SMD-01B Specifications
4.1. Reference Information about Package
4.1.1. Layout of SMD-01B Internal Components
The LED and OEIC are arranged as shown below.
The optical center is the point midway between the LED emitter and light receiver. See sections 2-1 and 2-2 forexamples.

[TOP VIEW]
LED Emitter

Light receiver / photodiode array
OEIC (built-in amp.)

SMD-01B Application Note
ANE240010-E001

2024.03
6/12

SMD-01B

Optical Encoder IC

4.1.2. Bottom Surface External View
The gray rectangular portion in the following diagram from the datasheet indicates the bottom surface insulation resin
portion, and is not an electrical terminal.

4.1.3. Environmental Data
The SMD-01B is a lead-free, PVC-free (polyvinyl chloride), Halogen-free, and RoHS compliant product.

SMD-01B Application Note
ANE240010-E001

2024.03
7/12

SMD-01B

Optical Encoder IC

4.2. Electrical Specifications Reference Information
4.2.1. Basic Connection
The SMD-01B operates with just power supply and setting terminal connections. However, bypass capacitors should
also be connected as shown below to counter environmental noise and in applications that require high accuracy. The
0.1μF capacitor should be positioned as close as possible to the SMD-01B. Ceramic bypass capacitors with excellent
frequency response are most suitable.

[Typical connection (VCC=5V supply, minimum LED current)]

4.2.2. Output Amplitude Adjustment[SMD-01B Electrical Characteristics Excerpt]
Parameter
SymbolConditions
A-phase output signal
VAP-P
amplitude
AB-phase output
Vp-p
VABP-Psignal amplitude
SWL1=H
SWL2=H
B-phase output signal
VBP-P*Reference scale
amplitude
BB-phase output
VBBP-Psignal amplitude

Min

Typ

Max

Unit

Terminal
VA
VAB

0.13

0.85

3.00

V
VB
VBB

The SMD-01B output signal specifications are outlined above.
If the output amplitude must be guaranteed to be above a certain value (for example, 0.3V), the LED luminosity foreach device can be adjusted to increase/decrease the output amplitude using the following trimming settings.
[Output Amplitude Multiplication Settings]
SWL1 terminal
H
H
SWL2 terminal
H
L
A,B-phase
output amplitude
×1.0
×1.8
multiplication*H = VCC level, L = GND level

L
H

L
L

×2.6

×0

Returning to the example, the SWL1 and SWL2 logic levels can be adjusted to ensure the output amplitude is set to
0.3V or higher.
Note that changing the LED current will also greatly affect the SMD-01B current consumption. Check the electricalcharacteristics to determine the current consumption under the desired operating conditions.
In practice, the output amplitude rarely approaches the maximum or minimum values published in the electrical
specifications. In almost all applications, the LED current can be set to the minimum value without problem.

SMD-01B Application Note
ANE240010-E001

2024.03
8/12

SMD-01B

Optical Encoder IC

4.2.3. Output Noise Measures: Differential Outputs
The SMD-01B outputs two sine wave signals (VA and VB) with a period of 20μm, and two inverted forms of thesesignals (VAB and VBB). There is a 90° phase difference between VA and VB, and between VAB and VBB.
The differential output of non-inverted and inverted signals for both A-phase and B-phase waveforms can be used toprevent external electric field interference that can cause common-mode noise.
A typical differential output connection is shown in the following figure.

The four analog signals have an offset from the Vref reference voltage output. Any external circuit connected to the
outputs must calibrate for these offsets.

SMD-01B Application Note
ANE240010-E001

2024.03
9/12

SMD-01B

Optical Encoder IC

4.3. Temperature Specifications Reference Information
The SMD-01B maximum storage temperature is 80°C. If the package is stored at temperatures higher than 80°C for an
extended length of time, the package resin will begin to discolor yellow and the output amplitude characteristics will
begin to deteriorate.
The maximum operating temperature is 60°C. The IC generates additional heat internally during operation, but will not
exceed 80°C even when the LED luminosity is set to maximum and is generating the maximum heat.
4.3.1. Operation at Ambient Temperatures Exceeding 60°C
When the LED luminosity is set to “Low” or “Medium” using SWL1 and SWL2, the internal heat generated by the
LED is limited, making operation possible at ambient temperatures higher than 60°C.
However, the relationship between IC and LED heat generation and device temperature is greatly influenced by themounting and other conditions, so careful evaluation should be carried out under all possible operating conditions.
SWL1
H
H
L

SWL2
H
L
H

Description“Low” LED luminosity, minimum heat generation“Medium” LED luminosity, medium heat generation“High” LED luminosity, 60°C operating temperature conditions

As an example, the device temperature may increase by 5 to 6°C, depending on operating conditions, when the LED
luminosity is set to “Low”.

SMD-01B Application Note
ANE240010-E001

2024.03
10/12

SMD-01B

Optical Encoder IC

5. Handling Precautions
Ensure the gray portion containing the LED and OEIC, shown in the
diagram, clean and free from dust and other contaminants.
If it is dirty, gently wipe the surface with a soft clean cloth dipped inmethanol or ethanol to remove all contaminants. The use of otherliquids or wiping vigorously may cause scratching, clouding, orotherwise damage the surface of the encoder. Exercise caution whencleaning the device surface.
Avoid direct contact with the SMD-01B and scale when handling,
installing, or adjusting.
Ensure that the operating temperature of any unit or housing
containing the SMD-01B will not exceed the temperature
specifications of the device.
The SMD-01B is designed to prevent external light interference. However, note that there is the potential that strong
localized light sources may affect the encoder output.
The light intensity of the SMD-01B built-in LED does not exceed the value for Class 1 standard visible LED eye
safety as prescribed by IEC60825-1.

6. USAGE AND PRECAUTIONSThis product is designed and manufactured to the generally accepted standards of reliability as expected for use ingeneral electronic and electrical equipment, such as personal equipment, machine tools, and measurement
equipment. This product is not designed and manufactured to be used in any other special equipment requiringextremely high level of reliability and safety, such as aerospace equipment, nuclear power control equipment, medical
equipment, transportation equipment, disaster prevention equipment, security equipment.
If you wish to use this product in equipment requiring extremely high level of reliability, please contact our sales
department or representative in advance.
In the event that this product is used in such equipment, please take scrupulous care and apply fail-safe techniques
including redundancy and malfunction prevention in order to prevent damage to life, health, property, or infrastructureetc. in case there is some malfunction in the product.

SMD-01B Application Note
ANE240010-E001

2024.03
11/12

SMD-01B

Optical Encoder ICThis Application Note is provided as a reference for product introduction and customer evaluation purposes for thisproduct. Typical characteristics and other values mentioned in this document are provided as reference data only todemonstrate principles and trends; this document does not include manufacturing tolerances and other characteristics
data. Devices should only be used after thorough evaluation under actual operating conditions.

Please pay your attention to the following points at time of using the products shown in this document.

1. The products shown in this document (hereinafter ”Products”) are designed and manufactured to the generally
accepted standards of reliability as expected for use in general electronic and electrical equipment, such as
personal equipment, machine tools and measurement equipment. The Products are not designed and manufactured
to be used in any other special equipment requiring extremely high level of reliability and safety, such as aerospaceequipment, nuclear power control equipment, medical equipment, transportation equipment, disaster prevention
equipment, security equipment. The Products are not designed and manufactured to be used for the apparatus thatexerts harmful influence on the human lives due to the defects, failure or malfunction of the Products.
If you wish to use the Products in that apparatus, please contact our sales section in advance.
In the event that the Products are used in such apparatus without our prior approval, we assume no responsibility
whatsoever for any damages resulting from the use of that apparatus.
2. NPC reserves the right to change the specifications of the Products in order to improve the characteristics orreliability thereof.
3. The information described in this document is presented only as a guide for using the Products. No responsibility is
assumed by us for any infringements of patents or other rights of the third parties which may result from its use. No
license is granted by implication or otherwise under any patents or other rights of the third parties. Then, we assume
no responsibility whatsoever for any damages resulting from that infringements.
4. The constant of each circuit shown in this document is described as an example, and it is not guaranteed about its
value of the mass production products.
5. In the case of that the Products in this document falls under the foreign exchange and foreign trade control law orother applicable laws and regulations, approval of the export to be based on those laws and regulations are necessary.
Customers are requested appropriately take steps to obtain required permissions or approvals from appropriate
government agencies.
6. When exporting customer’s products that use the Products, customers must comply with the "Foreign Exchange andForeign Trade Act" and other export-related laws and regulations, and follow the necessary procedures inaccordance with those laws and regulations. Do not use the Products in equipment whose sale is prohibited byexport-related laws and regulations ("JP Foreign Exchange and Foreign Trade Act" and "US Export Administration
Regulations", etc.). In addition, please do not sell the Products to users who are expected to use it for the above
equipment or companies in its supply chain. If a user who uses module parts and equipment using the Products is acompany suspected of violating human rights, please do not sell the above parts and equipment to that user

SEIKO NPC CORPORATION
2-9-4, Taito, Taito-ku,
Tokyo 110-0016, Japan
TEL +81-3-6747-5300
FAX +81-3-6747-5303
https://www.npc.co.jp/
Email: sales@npc.co.jp
SMD-01B Application Note
ANE240010-E001

2024.03
12/12